In general, the gas generating composition used for a vehicle airbag system comprises a fuel containing sodium azide as a base and an oxidizing agent. However, in view of toxicity of sodium azide and restrictions on the handling, various attempts have been made to find alternative to the mixture used for preparation of the sodium-azide-containing gas generant so far.
U.S. Pat. No. 5,783,773 discloses a composition comprising phase stabilized ammonium nitrate as an oxidizing agent, and triaminoguanidinenitrate (hereinafter it is abbreviated to “TAGN”) or combination of TAGN/guanidinenitrate as a fuel component. Further, U.S. Pat. No. 5,780,768 discloses a composition comprising guanidinenitrate/nitroguanidine as a fuel component and perchlorate as a base agent of the oxidizing agent. Both of the compositions are basically intended to obtain an adequate combustion speed by combining a high reactive component, such as TAGN and perchlorate, with a low reactive oxidizing agent and fuel. However, at the same time as the increase of the combustion speed, the calorific value increases also. In view of this, those gas generant compositions cannot be said to be suitable for the gas generator.
Japanese Patent Laid-open (Unexamined) Publication No. 2000-86375 discloses a combination of a fuel selected from compounds containing not less than 25% oxygen atom in a molecule by atomic weight, and a metal oxide and a metal compound oxide. Although this composition is designed to lower a combustion temperature, since the metal oxide is used for the oxidizing agent, the number of moles per weight of gas generated is not of sufficiency. When that composition is attempted to acquire a required number of moles of gas generated for inflating an airbag, an amount of gas generant used increases and, as a result, the calorific value generated by the combustion of the gas generant increases. This means that the gas generator using the composition of this type requires a large amount of coolants, so that it is hard to realize reduction in size and weight of that gas generator.
It is an object of the present invention to provide a gas generant composition that allows reduction in size and weight of a gas generator and provide a gas generator using that gas generant composition.